1. Field of the Invention
Embodiments of the present invention generally relate to the design and layout of a production line used to form a solar cell device. Embodiments of the present invention also generally relate to the design and selection of various apparatuses and processes that are useful for forming a solar cell device.
2. Description of the Related Art
Photovoltaic (PV) devices or solar cells are devices which convert sunlight into direct current (DC) electrical power. Typical thin film type PV devices, or thin film solar cells, have one or more p-i-n junctions. Each p-i-n junction comprises a p-type layer, an intrinsic type layer, and a n-type layer. When the p-i-n junction of the solar cell is exposed to sunlight (consisting of energy from photons), the sunlight is converted to electricity through the PV effect. Solar cells may be tiled into larger solar arrays. The solar arrays are created by connecting a number of solar cells and are then joined into panels with specific frames and connectors.
Typically, a thin film solar cell includes active regions and a transparent conductive oxide (TCO) film disposed as a front electrode and/or as a back electrode. The photoelectric conversion unit includes a p-type silicon layer, a n-type silicon layer, and an intrinsic type (i-type) silicon layer sandwiched between the p-type and n-type silicon layers. Several types of silicon films including microcrystalline silicon film (μc-Si), amorphous silicon film (a-Si), polycrystalline silicon film (poly-Si) and the like may be utilized to form the p-type, n-type, and/or i-type layers of the photoelectric conversion unit. The backside contact may contain one or more conductive layers. There is a need for an improved process of forming a solar cell that has good interfacial contact, low contact resistance and provides a high overall electrical device performance of the solar cells.
With traditional energy source prices on the rise, there is a need for a low cost way of producing electricity using a low cost solar cell device. Conventional solar cell manufacturing processes are highly labor intensive and have numerous interruptions that can affect production line throughput, solar cell cost and device yield. Conventional solar cell fabrication processes contain a number of manual operations that can cause the formed solar cell device properties to vary from one device to another. These manual processes are labor intensive, time consuming and costly. There is a need for a continuous non-interrupted flow of solar cell substrates through a solar cell production line to reduce cost and improve device yield. Thus, there is a need for a production line, or system, that is able to perform all phases of the solar cell fabrication process.
Also, there is a need for an apparatus and method of testing a solar cell device during different phases of the formation process to assure that the solar cells being formed in the production line are formed in a repeatable manner. Also, there is need for a testing module that can characterize the properties of a partially formed solar cell device to assure that its performance is within a desired performance range and that the combination of solar cell formation steps creates a solar cell device that meets the functional and performance specifications required by the solar cell device manufacturer.